import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Lily
 * Date: 2024-11-05
 * Time: 20:01
 */
public class test_3 {
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        char[] s = in.next().toCharArray();
        int n = s.length;
        int[][] dp = new int[n][n];
        for(int i = n - 1; i >= 0; i--)
        {
            dp[i][i] = 1;
            for(int j = i + 1; j < n; j++)
            {
                if(s[i] == s[j]) dp[i][j] = dp[i + 1][j - 1] + 2;
                else dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1]);
            }
        }
        System.out.println(dp[0][n - 1]);
    }
}
